The present invention relates to a synchronous coupling and, more particularly, a synchronous coupling having locking means.
With mechanically synchronized jaw couplings known in the prior art, for example from CH-PS 499735, driving engines or motors can be automatically coupled or uncoupled without the speed or the torque having to be monitored. In these cases, during synchronous operation, a synchronizing sleeve is displaced axially by ratchet teeth and during the engagement a screwing-in movement is transmitted via a pawl to a coupling star. As a result of this, helical screw-in teeth come into engagement and, after reaching an axial stop, transmit the torque.
The disengagement process for the coupling is initiated on a change in direction of rotation or acceleration of the output. This can be prevented, however, if the coupling star and the output shaft are positively connected to one another through adjusting teeth and locking teeth each constructed in the form of straight teeth.
A disadvantage in these cases, however, is that the locking teeth form a joint in the mechanical sense. As a result of the foregoing, during reverse operation, the torque is transmitted via the mechanically indeterminate double joint which is formed from the locking teeth and coupling teeth. This mode of operation is therefore only reliable for a short time. Alternating operating torques cannot be permitted to occur frequently because of the risk of wear of the teeth and of the synchronizing sleeve mounting.
A further coupling device is known from DE-OS 2430615 wherein an axial coupling consisting of two parts which are movable axially in relation to one another and an intermediate member transmitting torque wherein provided between the intermediate member and each of the two coupling parts are helical teeth which have a different pitch and are so directed that on the transmission of torque, a force develops which pulls the parts of the coupling together. In this case, the centering is effected via corresponding tapered surfaces on the coupling parts. In this case, the transmission of torque is only possible in one direction.
Accordingly, it is the primary object of the present invention to provide a synchronous coupling which is of simple construction and which permits operation with alternating torques without suffering from the disadvantages noted above.